Fatty alcohols represent important raw materials for various types of consumer products, for example cosmetics and detergents. Typically, they are obtained from vegetable oils for example by transesterification with methanol to form methyl esters and subsequent hydrogenation. The methyl esters for example from coconut or palm kernel oil are typically split into fractions C6-10, C12-14 and C16-18 by distillation in fractionation columns under vacuum. The different fractions are then hydrogenated separately.
In the hydrogenation step the methyl esters are converted to fatty alcohols and methanol. Due to side reactions additional by-products are formed such as for example water, hydrocarbons and wax esters. Furthermore, since the hydrogenation conversion is not 100% complete, residual methyl esters are remaining in the crude fatty alcohol fractions. Obviously, it is desirous to remove these unwanted by-products to a level which is acceptable in terms of the later conversion or application.
On known process involves removing methanol and water from the crude fatty alcohols by stripping in a simple flash distillation unit. In order to separate also other low boilers like hydrocarbons and remaining traces of methanol and water, an additional fractionation in a top cut column is typically applied. For removal of high boilers such as wax esters the fatty alcohols are further fractionated in an overhead distillation column. Alternatively the fatty alcohols can be purified in one column with side stream withdrawal. As a matter of fact, these standard operations require a lot of energy and technical equipment. Also, the waste material, although having a high content of organics, does not have any application and is typically used as an—quite expensive—fuel for generating steam and energy.